How to Avoid "String Too Long" Using PICTURE$ Function (36349)

SUMMARY

This article applies to Macintosh QuickBASIC Version 1.00 for the Apple Macintosh.

When collecting a large picture with the PICTURE ON...PICTURE OFF statements, the size of the picture may grow beyond the 32K maximum size allowed for a string variable. When the picture is assigned to a string variable with p$ = PICTURE$, a "String too long", error 15 message will appear if the recorded picture has exceeded 32,767 bytes.

The subprogram below allows you to monitor the current size of the picture that is being recorded. This allows you to stop recording and start a new picture when the size of the current picture approaches the limit for a BASIC string.

MORE INFORMATION

In the 64K ROM Macintoshes, QuickDraw pictures were limited to 32,767 bytes, but in the newer, 128K ROM (enhanced) Macintoshes, they are no longer restricted in size.

The following is a code example:

PICTURE ON  ' Turn on recording of the picture in heap space.
size& = 0
WHILE size& < 32700    'leave some margin
    PSET(RND*400+100,RND*400+100)  ' Draw a pixel at a random location.
    GetPictureSize size&  ' SUBprogram returns current picture size.
WEND
PICTURE OFF  ' Turn off recording of the picture in heap space.
p$ = PICTURE$    'get picture into a BASIC string
PICTURE ,p$      'draw the recorded picture
WHILE MOUSE(0) <> 1 : WEND    'wait for mouse click
END
' This SUBprogram returns the size of the picture currently recording:
SUB GetPictureSize( Size& ) STATIC
    hPic& = PEEKL( PEEKL(PEEKL(PEEKL(&H904))) + &H5C )
    IF hPic& <> 0 THEN    'return size of picture
        size& = PEEKW(PEEKL(PEEKL(PEEKL(hPic&))))
    ELSE    'no picture being recorded
        size& = 0
    END IF
END SUB